CAAS PPL Practice Tests

Questions & Explained Answers

CAAS PPL Meteorology Practice Questions, with Explained Answers

All 43 of our Meteorology practice questions, each shown with the correct answer and a short explanation of the reasoning behind it. Use it to revise, to check your working after a quiz, or to learn the theory the way the CAAS PPL exam tests it.

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  1. Q1. Oxygen and Nitrogen form a large part of the composition of air. What is the approximate proportion of other gases?

    • 10%
    • 5%
    • 3%
    • 1%Correct answer
    Why: Dry air is roughly 78% nitrogen and 21% oxygen, which together account for about 99% of the volume. That leaves only around 1% for all the other constituents combined, chiefly argon plus small amounts of carbon dioxide and trace gases.

  2. Q2. In which conditions would diurnal variations of surface temperature would be greatest in temperate latitudes?

    • Cloudy Skies and Light Winds
    • Clear Skies and Light WindsCorrect answer
    • Cloudy Skies and Moderate Winds
    • Clear Skies and Moderate Winds
    Why: The day/night temperature swing is largest under clear skies and light winds. Cloud would trap outgoing radiation at night and reflect incoming radiation by day, while strong wind mixes the surface air with the layer above; removing both lets the ground heat and cool to extremes.

  3. Q3. During periods of settled weather, the variation in temperature throughout the day (24hrs) shows a more or less consistent pattern. The effect of this diurnal (daily) temperature variation is that the coldest part of the day is;

    • Mid-Morning and hottest part is around midday
    • Before dawn and the hottest part is around midday
    • Before dawn and the hottest part is around late afternoonCorrect answer
    • Around dawn and the hottest part is around early afternoon
    Why: The surface keeps losing heat by radiation right up until sunrise, so the coldest point is just before dawn. After noon the ground still receives more heat than it loses for a few hours, so peak temperature lags the sun and occurs in the late afternoon.

  4. Q4. Inversions develop when the temperature in a layer of air;

    • Remains Constant
    • Increases with HeightCorrect answer
    • Drops below 0 degrees celsius
    • Decreases with Height
    Why: Normally temperature falls with height, so an inversion is the reverse: a layer in which temperature increases with height. This warm-over-cold arrangement is very stable and resists vertical mixing, trapping moisture and pollutants beneath it.
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  5. Q5. Which of the areas described below will show you the largest diurnal variation in temperature?

    • An inland basin or valley in winter because of the very low temperature experienced just before dawn
    • A desert area where skies are clearCorrect answer
    • A heavily forested area because trees modify the local climate
    • An oceanic area because the sea does not cool at night
    Why: A clear-sky desert shows the greatest diurnal range. Dry, cloudless air lets intense solar heating by day and rapid radiative cooling by night occur unchecked, and the dry ground has little thermal capacity to moderate the swing, unlike the sea or moist, forested or cloudy regions.

  6. Q6. In the lower stratosphere, the temperature:

    • Constant at approximately -56 degrees celsiusCorrect answer
    • Increases steadily throughout the layer
    • Constant at approximately 15 degrees celsius
    • Decreases steadily throughout the layer
    Why: Above the tropopause the temperature stops falling and becomes roughly isothermal through the lower stratosphere, holding near the ISA tropopause value of about -56.5°C before rising higher up due to ozone absorption. Hence it stays approximately constant at around -56°C.

  7. Q7. After sunset, terrestrial radiation over land accompanied by light mixing wind may cause?

    • A radiation inversion of the air aboveCorrect answer
    • Low stratiform cloud to form
    • Mist
    • Advection Fog
    Why: After sunset the ground cools by radiation, chilling the air in contact with it. A light wind mixes this cooling through a shallow layer rather than letting fog form at the surface, producing a radiation (nocturnal) inversion with warmer air sitting above the cooled layer.

  8. Q8. QNH is calculated by reducing airfield pressure to MSL. This is achieved by using:

    • ISACorrect answer
    • Pressure Altitude
    • Jet Standard Atmosphere
    • IATA Standard Atmosphere
    Why: QNH converts the measured airfield pressure to its mean-sea-level equivalent by assuming the temperature and density of the International Standard Atmosphere through the fictitious column of air below the station. ISA provides the standard relationship between pressure and height used for that reduction.

  9. Q9. A low-pressure system with a cold air core typically intensifies with height. This is because the air in the cold core is:

    • Moist and therefore has Low Pressure Lapse Rate
    • Moist and therefore has a High Pressure Lapse Rate
    • Less Dense
    • More DenseCorrect answer
    Why: Cold air is denser, so pressure falls off more rapidly with height through a cold core. A low at the surface therefore deepens and becomes more pronounced aloft, because the dense cold air produces a steeper vertical pressure gradient than warmer surroundings.

  10. Q10. The relationship between surface pressure centres and pressure centres aloft is dependent on the:

    • Surface Humidity
    • Stability of the Column of Air
    • Surface Pressure
    • Temperature of the Column of AirCorrect answer
    Why: Whether a surface pressure centre persists, strengthens or reverses with height depends on the temperature of the air column, because temperature governs density and hence how quickly pressure decreases with altitude. Cold columns intensify lows aloft; warm columns favour highs aloft.

  11. Q11. What is the MSL Air Density in ISA?

    • 925g/m3
    • 1.025g/m3
    • 1125g/m3
    • 1.225g/m3Correct answer
    Why: The International Standard Atmosphere defines mean-sea-level air density as 1.225 kg/m³ (1225 g/m³), paired with 15°C and 1013.25 hPa. This is the reference density used for performance and instrument calibration.

  12. Q12. ISA assumes that at MSL, Air Temperature is:

    • 12 degrees celsius
    • 13 degrees celsius
    • 15 degrees celsiusCorrect answer
    • 18 degrees celsius
    Why: The International Standard Atmosphere fixes mean-sea-level temperature at 15°C, together with a pressure of 1013.25 hPa and density of 1.225 kg/m³. These reference values let aircraft performance and altimetry be standardised worldwide.

  13. Q13. An aircraft is parked on an airfield 702ft above MSL, How could the pilot estimate the QNH using the aircraft altimeter?

    • Set the altimeter to 0 and read the pressure of the subscale
    • Set the sub-scale to 1013 hPa and use the standard setting
    • Set the altimeter to 702ft and correct for ambient temperature at 120ft per degree centigrade
    • Set the altimeter to 702ft and read the pressure off the subscaleCorrect answer
    Why: On the ground the altimeter reads correct height when set to QNH, so the pilot winds the sub-scale until the needle indicates the known field elevation of 702 ft. The pressure then shown in the sub-scale window is the QNH.

  14. Q14. What is an example of the term “FL340”?

    • A height of 34,000ft AMSL
    • Altitude of the 250 hPa level
    • A Pressure Altitude of 34,000ftCorrect answer
    • The altitude of the 250 hPa level when density is taken into account
    Why: A flight level is an altitude flown with the altimeter set to the standard 1013.25 hPa, i.e. a pressure altitude. FL340 therefore means a pressure altitude of 34,000 ft, not a true height above sea level, which varies with the actual pressure and temperature.

  15. Q15. If the sea level pressure is 1,000 hPa, what is the pressure at 1,500ft?

    • 900 hPa
    • 970 hPaCorrect answer
    • 1000 hPa
    • 1010 hPa
    Why: Near sea level pressure falls roughly 1 hPa for every 30 ft of climb. Over 1500 ft that is about 50 hPa, so from a 1000 hPa sea-level value the pressure at 1500 ft is approximately 970 hPa.

  16. Q16. Wind speeds are usually highest when:

    • Temperature Gradient is Constant
    • Pressure Gradient is weak
    • Isobars are Straight
    • Pressure Gradient is StrongCorrect answer
    Why: Wind is driven by the pressure-gradient force, which is proportional to how tightly the isobars are packed. A strong pressure gradient (closely spaced isobars) produces the strongest winds; a weak gradient gives light winds.

  17. Q17. The effect due to the earth’s rotation is responsible for the deflection of wind flow away from high to low pressure is known as:

    • Pressure Gradient Force
    • Centripetal Force
    • Coriolis ForceCorrect answer
    • Centrifugal Force
    Why: The apparent deflecting effect arising from the Earth's rotation is the Coriolis force. It acts at right angles to the wind, turning moving air to the right in the northern hemisphere and to the left in the southern, so air does not flow straight from high to low pressure.

  18. Q18. The force which causes air moving towards an area of low pressure to be deflected due to the earth’s rotation of the earth is?

    • Centrifugal Force
    • Geostrophic Force
    • Coriolis ForceCorrect answer
    • Gradient Force
    Why: Air moving toward low pressure is deflected by the Coriolis force, which results from the Earth's rotation. Acting perpendicular to the motion, it is the reason wind circulates around pressure systems rather than flowing directly down the pressure gradient.

  19. Q19. An area of low-level convergence in the southern hemisphere will be recognised by?

    • Frontal Activity, Decreasing Pressure and Light Winds with No Precipitation
    • Increasing Turbulence, Lowering Air pressure and Increasing Cloud with Possible PrecipitationCorrect answer
    • Significant Local Effort, Clear skies and Light Winds with Lowering Air Pressure
    • Decreasing Turbulence, Increasing Air Pressure and Decreasing Cloud with Clear Skies
    Why: Where surface air converges it is forced to rise, cooling and condensing as it ascends. The signs are therefore increasing turbulence, falling pressure and building cloud with possible precipitation, regardless of hemisphere.

  20. Q20. Which of the following options best defines wind and how is it measured?

    • Wind is the Movement of air either horizontally or vertically which is caused by vapor in the atmosphere and is measured in knots.
    • Wind is the horizontal movement of air caused by isobaric inversion and is measured by Radiosondes.
    • Wind is the horizontal movement of air caused by air pressure differences and is normally measured by an anemometer.Correct answer
    • Wind is the movement of air caused by low pressure weather systems which causes a gravitational pull on the surrounding air to a central core. It is measured by an anemometer which indicates direction by the clock reference.
    Why: Wind is the largely horizontal movement of air produced by differences in atmospheric pressure, air flowing from higher to lower pressure. It is routinely measured at the surface by an anemometer, which records wind speed (and, with a vane, direction).

  21. Q21. In the atmosphere, what is the layer above the tropopause?

    • StratosphereCorrect answer
    • Ionosphere
    • Mesosphere
    • Troposphere
    Why: The tropopause is the boundary marking the top of the troposphere; the layer immediately above it is the stratosphere, where temperature is initially isothermal and then increases with height due to ozone absorbing ultraviolet radiation.

  22. Q22. What does gradient wind follow?

    • Pressure gradient force
    • Curved isobarsCorrect answer
    • Straight isabars
    • Coriolis effect
    Why: The gradient wind is the balanced flow that follows curved isobars around pressure systems, where the pressure-gradient, Coriolis and centripetal forces are in balance. The geostrophic wind, by contrast, applies to straight isobars.

  23. Q23. Clouds__ some of the incoming solar radiation, which in turn___ the ___daily temperature

    • reflect; increases ; maxCorrect answer
    • absorb; increases ; min
    • reflect ; decreases ; max
    • absorb ; decreases ; min
    Why: Cloud reflects a portion of incoming solar radiation back to space, reducing daytime heating of the surface. This lowers the maximum daily temperature, which is why cloudy days are typically cooler than clear ones.

  24. Q24. What is the relationship between pressure, temperature and air density?

    • low pressure & cold temp = low density
    • high pressure & warm temp = low density
    • high pressure & cold temp = high densityCorrect answer
    • low pressure & warm temp = high density
    Why: From the gas law, density is proportional to pressure and inversely proportional to temperature. High pressure packs molecules closer together and low (cold) temperature reduces their spacing too, so high pressure combined with cold temperature gives the highest air density.

  25. Q25. In the troposphere temperature has the following action:

    • It increase throughout the layer
    • It decreases throughout the layerCorrect answer
    • It has a temperature inversion
    • It remains constant at 15c at the surface
    Why: The troposphere is heated mainly from below by the surface, so on average temperature decreases steadily with height throughout the layer (about 1.98°C per 1000 ft in ISA) up to the tropopause.

  26. Q26. In the Stratosphere:

    • The temperature stays constant at about -56 degrees CelsiusCorrect answer
    • Temperature increases
    • Temperature decreases
    Why: Through the lower stratosphere the temperature is essentially isothermal, holding close to the ISA tropopause value of roughly -56°C, before rising at greater heights where ozone absorbs solar ultraviolet. Hence it stays about constant near -56°C.

  27. Q27. What are the functions of a barometer?

    • Measure altitude
    • Measure weight of air above a pointCorrect answer
    • Measure weight of air corrected for temperature
    Why: A barometer measures atmospheric pressure, which is simply the weight of the column of air above the point of measurement. An altimeter is really a barometer calibrated to display height from that pressure.

  28. Q28. Atmoshperic pressure ______, as height _____

    • Decreases, IncreasesCorrect answer
    • Increases, Decreases
    • Stays constant, Icreases
    Why: Atmospheric pressure is the weight of air above a level, so as height increases there is less air above and the pressure decreases. The fall is rapid low down (about 1 hPa per 30 ft near the surface) and slower at altitude.

  29. Q29. As compared to gradient wind, surace wind is reduced and hits the isobar at an angle. What cuases this?

    • Pressure gredient
    • Increased coriolis force
    • Surface frictionCorrect answer
    Why: Near the ground, surface friction slows the wind. A weaker wind generates less Coriolis force, so the balance shifts and the wind backs to cross the isobars at an angle toward low pressure, instead of blowing parallel to them as it does aloft.

  30. Q30. Degree or intensity of heat is associated with which property:

    • Kinetic energy
    • Potential energy
    • Adiabatic energy
    • TemperatureCorrect answer
    Why: Temperature is the property that expresses the degree or intensity of heat of a substance. It reflects the average kinetic energy of the molecules, but the measurable degree of hotness itself is temperature.

  31. Q31. A low-level system with cold air typically intensifies with height because:

    • Air is moist with higher pressure lapse rate
    • Air is moist with lower pressure lapse rate
    • Air is denserCorrect answer
    • Air is less dense
    Why: Cold air is denser, so pressure decreases more rapidly with height through it. A surface low with a cold core therefore intensifies aloft, because the dense cold air creates a steeper vertical pressure gradient than the warmer surroundings.

  32. Q32. Balance of pressure gradient force, centrifugal force, and coriolis force result in curved winds blowing parallel to isobars:

    • Gradient windsCorrect answer
    • Geostrophic winds
    • Surface winds
    Why: When the pressure-gradient, Coriolis and centrifugal forces balance around curved isobars, the resulting flow parallel to those isobars is the gradient wind. The geostrophic wind is the equivalent balance for straight isobars without the centrifugal term.

  33. Q33. Wind is defined as

    • Movement of air in atmosphere due to pressure differences, with speed and direction measured in nautical miles per hourCorrect answer
    • Movement of air in atmosphere due to temperature differences, with speed only measured in nautical miles per hour
    • Movement of air in atmosphere due to temperature differences, with speed and direction measured in nautical miles per hour
    • Movement of air in atmosphere due to rotation of earth, with speed and direction measured in nautical miles per hour
    Why: Wind is the horizontal movement of air from high to low pressure, driven by the pressure-gradient force that arises from differences in atmospheric pressure. In aviation, wind speed is reported in knots, i.e. nautical miles per hour.

  34. Q34. An area of low pressure in the summer is indicated by ______ pressure and ______ aloft

    • Low, DivergenceCorrect answer
    • Low, Convergence
    • High, Divergence
    • High, Convergence
    Why: A surface low is maintained by air rising and diverging outward aloft, which removes mass from the column and keeps surface pressure low. So a summer low shows low pressure at the surface with divergence above it.

  35. Q35. Which statement best describes the relationship between pressure temperature and density

    • Density increase, pressure increase and temperature increase
    • Density increase, pressure decrease and temperature increase
    • Density increase, pressure decrease and temperature decrease
    • Density increase, pressure increase and temperature decreaseCorrect answer
    Why: By the gas law, density is proportional to pressure but inversely proportional to temperature. Density therefore rises when pressure increases and temperature falls; a rise in temperature would instead lower density, which is why the all-increasing option is physically inconsistent.

  36. Q36. What are 'ISA conditions'?

    • 15 Degrees C, 1013.2hPa.Correct answer
    • 15 Degrees F, 1013.2hPa
    • 15 Degrees C, 28.92Hg
    • 15 Degrees F, 28.92Hg
    Why: The International Standard Atmosphere defines mean-sea-level conditions as 15°C and 1013.2 hPa (with density 1.225 kg/m³). These reference values, expressed here in degrees Celsius and hectopascals, standardise altimetry and performance calculations.

  37. Q37. When is coldest and hottest time of the day?

    • Before dawn and at midday
    • After dawn and at Midday
    • After dawn when the sun rises and after midday
    • Before dawn and a few hours after middayCorrect answer
    Why: The surface keeps losing heat by radiation all night, so the minimum temperature occurs around or just before dawn. After noon the ground still gains more heat than it loses for a few hours, so the daily maximum lags solar noon and occurs in the mid-to-late afternoon, not at midday.

  38. Q38. Conditional Stability of the atmosphere is a state where the Environmental Lapse Rate (ELR):

    • Lies between saturated adiabatic lapse rate & dry adiabatic lapse rateCorrect answer
    • Is greater than both the saturated adiabatic lapse rate & dry adiabatic lapse rate
    • Is the same as both saturated adiabatic lapse rate & dry adiabatic lapse rate
    • Is less than both the saturated adiabatic lapse rate & dry adiabatic lapse rate
    Why: Conditional instability exists when the environmental lapse rate lies between the saturated and dry adiabatic lapse rates. Such air is stable while unsaturated (the dry rate cools rising air faster than the environment) but becomes unstable once saturated, the condition being whether the air reaches saturation.

  39. Q39. The aircraft altimeter measures:

    • Altitude by calibrating magnitude of vertical pressure deviations and indicating altitude above sea level
    • Atmospheric pressure and calibrated to indicate separation from a sea level pressure datumCorrect answer
    • Altitude by process of measuring rate of decrease in pressure
    • Atmospheric density
    Why: An altimeter is essentially an aneroid barometer that senses atmospheric pressure and is calibrated, against a sub-scale datum, to display the height separation from a chosen sea-level pressure. It reads pressure, not density or rate of change, and converts it to an indicated altitude.

  40. Q40. Temperature lapse rate in troposphere in ISA is:

    • Decrease of 1.98 degrees /1000 feet up to 36090 AMSLCorrect answer
    • Decrease of 1.98 degrees /1000 feet until -56.5 degrees
    • Decrease of 1.5 degrees /1000 feet until -56.5 degrees
    • Decrease of 3 degrees /1000 feet
    Why: In the International Standard Atmosphere temperature falls at 1.98°C per 1000 ft throughout the troposphere, up to the tropopause at 36,090 ft, where it levels off at about -56.5°C and the stratosphere begins.

  41. Q41. Relationship of surface pressure centres and pressure centres aloft depends on:

    • Surface pressure
    • Stability of column of air
    • Temperature of column of airCorrect answer
    • Surface humidity
    Why: How a surface pressure centre relates to the pressure pattern aloft is governed by the temperature of the air column, since temperature sets the density and therefore the rate at which pressure decreases with height. Cold columns deepen lows aloft; warm columns build highs aloft.

  42. Q42. If a plane is parked at 720ft above mean sea level, how can the pilot estimate the QNH?

    • Setting 720ft in the altimeter and reading off the sub scaleCorrect answer
    • Setting 0ft in the altimeter and reading off the sub scale
    • Setting 1013.25 in the subscale and taking the reading
    • Setting 720 then compensating (some number) for humidity
    Why: On the ground the altimeter indicates correct height when set to QNH, so the pilot adjusts the sub-scale until the needle reads the known field elevation of 720 ft. The value then displayed in the sub-scale window is the QNH.

  43. Q43. After sunset, terrestrial radiation over land accompanied by a light mixing wind may cause:

    • A radiation inversion of the air aboveCorrect answer
    • Advection fog
    • Mist
    • Low stratiform cloud
    Why: After sunset the ground cools by radiation and chills the air touching it. A light wind stirs this cooling through a shallow layer instead of allowing surface fog, producing a radiation (nocturnal) inversion with warmer air lying above the cooled layer.

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